This procedure frees memory that was previously allocated with Allocate. pointer must be a valid pointer. After the procedure returns, pointer will be rendered invalid (pointing to an invalid memory address), and its use (dereferencing or calling Deallocate again) will result in undefined behavior.

Calling Deallocate on a null pointer induces no action.

Deallocate is an alias for the C runtime library's free, so it's not guaranteed to be thread safe in all platforms.

Examples:
The following example shows how to free previously allocated memory. Note that the pointer is set to null following the deallocation:

Deallocate( integerPtr )'' free memory back to system
integerPtr = 0'' and zero the pointerEnd Sub

DeallocateExample1()End0

Although in this case it is unnecessary since the function immediately exits afterwards, setting the pointer to null is a good habit to get into. If the function deallocated memory from a pointer that was passed in by reference, for instance, the pointer that was used in the function call will be rendered invalid, and it is up to the caller to either reassign the pointer or set it to null. Example 3 shows how to correctly handle this kind of situation, and the next example shows the effects of deallocating memory with multiple references.

In the following example, a different pointer is used to free previously allocated memory.

Note that after the deallocation, both pointers are rendered invalid. This illustrates another one of the ways that bugs can arise when working with pointers. As a general rule, only deallocate memory previously allocated when you know that there is only one (1) pointer currently pointing at it.

In the program above, a reference pointer in a function is set to null after deallocating the memory it points to. An ASSERT macro is used to test if the original pointer is in fact null after the function call. This example implies the correct way to pass pointers to functions that deallocate the memory they point to is by reference.

Dialect Differences:

Not available in the -lang qb dialect unless referenced with the alias __Deallocate.